Tribochemical study of hydrogenated and nitrogenated carbon overcoats at the head-disk interface in magnetic hard drives

This dissertation focuses on studies of the tribochemistry at the head-disk interface in a computer hard disk drive. Effort is made to understand the wear mechanisms and friction at the interface and to find ways to enhance the wear durability.; Standard accelerated wear testers are used to conduct the contact-start-stop tests and drag tests in air. A tribochemical tester equipped with a mass spectrometer is used to conduct the drag tests in ultra-high vacuum. This tribochemical tester can be used to monitor the tribochemistry at the head-disk interface in real time with the friction measurement.; Results in this dissertation show that depositing carbon films on {dollar}rm Alsb2Osb3/TiC{dollar} sliders' air bearing surfaces can significantly improve the wear durability at the interface. Tribochemical studies are carried out to investigate this phenomenon. Different wear mechanisms are found for the coated and uncoated sliders. The carbon coatings on the sliders can protect lubricant better which results in improvement in wear durability at the head-disk interface.; Increasing the hydrogen content in the disk carbon coating can also help improve the wear durability at the interface. It is demonstrated that a higher hydrogen content can help resist the chemical reaction between the slider materials and the lubricant.; Correlation between magnitude of friction and intensity of lubricant degradation is observed when no change in lubricant degradation mechanism occurs during the drag tests.; Nitrogenated carbon coatings on disks and sliders are evaluated. Their tribological performances are compared with those of hydrogenated carbon coatings. Results suggest that nitrogenated carbon coatings perform better on disks but not on the sliders' air bearing surfaces.; A SiC slider is also studied. Tests are conducted to compare the tribological performance of these sliders with that of {dollar}rm Alsb2Osb3/TiC{dollar} sliders in the tribochemical tester.